Preparation of beta-oxo esters



Patented Oct. 24, 195

UNITED STATES PATENT OFFICE 2,527,306

"PREPARATION BETA-OX0 ESTERS Isaac F. Halv-crstadt, Berkeley, Calif., assign-0r to American Cyanarnid Company, New York, N. Y., a corporation of Maine No Drawing. Application May 1, 1947, SerialNo. 745,243

. 1 I The present invention relates to the preparation'of beta-0x0 carboxylic acid esters. More particularly it relates to a methodof preparing betaoxo monocarboxylic acid esters and aralkyl betaoxo monocarboxylic acid esters.

The compounds prepared by the process of the present invention can be illustrated by the following general formula I in which R is an alkyl or an aralkyl radical and B'is an alkyl radical.

The compounds'are prepared by heating an alpha, gamma dioxo monocarboxylic acid ester to a relatively high temperature in the presence of a substance having a large surface area per unit volume. The preferred substance is ground glass. However, other substances can be used such as sodium formate, sodium chloride, activated carbon, coke, pumice, and the like or mixtures thereof. v

The reaction can be carried out usin a number of intermediates. Among these may be menture of from about 175 to about 250 C. How

ever, the reaction can be carried out at a temperature of from about 150 to about 275 C. depending somewhat on the intermediate used.

The reaction when conducted as a batch process is completed generally in from about minutes to about 4 hours. However, the time may be somewhat longer, up to 6 hours or more, depending upon the reactant and temperature used :in the reaction. The reaction can, also, be conducted practicall instantaneously by heating to :a relatively high temperature the substance having a large surface area in a tube into which the intermediate is fed at one end and the product recovered at the other end.

' beta-0x0 monocarboxylic acid esters.

and 2 g. of ground soft glass was heated ata te m- 4 Claims, (01. 260-483) The compounds of the present invention are useful as intermediates in the preparation of substituted thiouracils such as those described in co-.- pending application Serial No. 602,420, filed June 29, 1945, now abandoned. They are, a1so,Va1uable as intermediates in the preparation of substituted 4-oxo-6-alkyl pyrimidines and similar compounds. I

The following examples illustrate in greater particularity the method of preparing the various It will'be understood that these examples are given for purposes of illustrating preferred processes and are not to be construed as limiting the invention to the processes described therein,

2 Example .I

'CHa'CHzCHzCHrPLOCHs A mixture of 17.2 g. of methyl butyropyruvate perature of about 240 C. (bath temperature 355 C.) for approximately 3 hours The mixture obtained was then redistilled and the fraction boiling at to C./14 mm. was collected. The product obtained was methyl beta-oxo-caproate. The identity of the product was proved by reaction with thiourea which gave the product 6- propyl-Z-thiouracil.

Example II 1] I H CH3CHICCH2COCH3 A mixture of 15.8 g. of methyl propionopyruvate and 2 g. of ground soft glass was distilled as rapidly aspossible at a temperature of about 210 C. The mixture obtained was redistilled and the fraction, with boiling point 60-65/14 mm. Was collected. The product obtained was methyl beta oxo-valerate. The copper salt of this compound was prepared and had a melting point of to 157 C. This is very close to the melting point of the copper salt of methyl beta-oxo-valerate as reported in the literature.

Example III R omnodcmdoom A mixture of 950 g. (5.1 mol) of methyl deltadimethyl-alpha, gamma dioxocaproate and 100 g. of powdered soft glass (50%100 mesh and 50 200 mesh) was subject to pyrolysis at about C. After 1 hour 37% of the carbon monoxide was 3 evolved, after 2 hdur's 80% and after 5 hours the theoretical amount was evolved. After completion of pyrolysis the mixture was distilled and the fraction boiling at 90 to 94 C. (20 mm.) was collected. A yield of 643 g. (4.08 mol) 80% of methyl gamma-dimethyl-beta XoVa1erate was obtained.

To a mixture of 5 liters of methanol and mols of sodium metal was added 765 g. of the compound obtained above and 513 of thiourea. The total mixture was heated to reflux with steam.

A precipitate formed after 45 minutes and heat-.

ing was continued for 5 hours. The product obtained after several recrystallizations and further purification was 350 g. of S-tertiary butyl-2 thio- Example IV H II C H27C CHzC O CHa To 3.2 g. of methyl myristyl-pyruvate was added 2 g. of ground soft glass and the mixture heated gradually to 204 C., but kept mostly at 185 C. for about 4 hours. The residual liquid was distilled and the distillate on cooling solidified, The solid was then recrystallized from dilute ethanol and the product, methyl beta-oxo-tridecylpropionate, had a melting point of 34 to 35C. v

' I claim:

uracil having a melting point of 178 to 179 0..

1. A method of preparing compounds having the general formula 0 acm ocni in which R is a lower alkyl radical which comprises heating a compound having the formula:

u it RC 01120 CO CHa in which R is as defined above, in the presence of ground glass at a temperature of about 150 C. to about 275 C. for from about 10 minutes to about 4 hours.

2. A method of preparing methyl beta-0x0- caproate which comprises heating methyl butyropyruvate in the presence of ground glass at a temperature of about 175 C. to about 250 C. for from about 10 minutes to about 4 hours.

3. A method of preparing methyl beta-0x0- valerate which comprises heating methyl propionopyruvate in the presence of ground glass at a temperature of about C. to about 250 C. for from about 10 minutes to about 4 hours.

4. A method of preparing methyl gamma-dimethyl-beta-oxovalerate which comprises heating methyl delta-dimethyl-alpha,gamma-dioxocaproate in the presenc of ground glass at a temperature of about 175 C. to about 250 C. for from about 10 minutes to about 4 hours.

ISAAC F. HALVERSTADT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Altwegg et a1 Feb. 3, 1925 OTHER REFERENCES Hurd, Pyrolysis of Carbon Compounds (1929), pages 556-558, published by Chemical Catalog Co., New York, N. Y.

Number 

1. A METHOD OF PREPARING COMPOUNDS HAVING THE GENERAL FORMULA 